1. Technical Field
The present invention relates to a pre-treatment liquid and an image forming method using the pre-treatment liquid.
2. Description of the Related Art
Image forming methods using aqueous inkjet use a recording medium having a coating layer such as offset printing papers to form glossy images thereon. However, the aqueous ink is difficult to penetrate the recording medium while easy to penetrate a recording medium without a coating layer, and therefore droplets become one on the surface of the recording medium, resulting in an ink having a different color or bleeding between the recording medium and the ink. The bleeding causes a large problem of glossiness of the surface of an image after formed particularly in one pass images in an inkjet high-speed ream book field such as industrial fields. Adaptability between the aqueous ink and the recording medium on a recording medium having a coating layer such as coated papers is not sufficiently ensured. Therefore, matching between the aqueous ink and the recording medium is ensured with exclusive papers. However, this limits the recording media.
As another method, a method of applying a pre-treatment liquid capable of agglutinating or fixing a pigment in the ink on a recording medium having a coating layer just before discharging an ink is disclosed to prevent images from bleeding.
Japanese published unexamined application No. JP-2010-105187-A discloses a recording method of transferring a resin liquid including a particulate thermoplastic resin and an ink composition on a recording medium to print thereon. Japanese published unexamined application No. JP-2011-173411-A discloses an inkjet recording method of transferring a reaction liquid including an organic ammonium salt and a water-soluble cation polymer and an ink composition including a colorant and a resin emulsion on a recording medium to print thereon.
Japanese published unexamined application No. JP-2010-69634-A discloses using a treatment liquid including epihalohydrin and an amine copolymer as a cohesion promoter of an ink component.
The conventional recording methods using a pre-treatment liquid consume a large amount of the pre-treatment liquid to ensure image quality in applications such as high-speed ream book machines. In this case, between application of the pre-treatment liquid and discharge of the ink, the pre-treatment liquid contacts a transfer member and transfers thereto, resulting in problems such as damages thereof, retransfer due to accumulation of contamination and image quality deterioration such as back transfer. Further, a coated paper may deteriorate in strength of its coating layer due to the pre-treatment liquid.
In order to solve this problem, the pre-treatment liquid is dried after applied. This solves the transfer of the pre-treatment liquid, but causes other problems such as deterioration of cohesion ability of the pre-treatment liquid. Further, the present inventors found printed images deteriorate in glossiness after pretreated.
Because of these reasons, a need exists for a pre-treatment liquid capable of preventing deterioration of granularity and glossiness of images formed on a recording medium having a coating layer with an aqueous ink after the pre-treatment liquid is applied thereon and dried.